Find Prius fuel consumption as per JC08 standards for Prius in excellent condition below:
Fuel consumption compared with the 10 ? 15 mode and JC08 mode
2014 January I was compared for the current major models.
It should be noted that even in the same vehicle type, fuel consumption is slightly different due to differences in grade and equipment, etc.. For the correspondence grade of each model in the table refer to the item column of "corresponding car name Model grade".
Car name (link to article) 10 ? 15 mode JC08 mode Corresponding car name Model grade Models Overview
Toyota Prius c 37.0km / L DAA-NHP10 type: Full Grade Hybrid car
Honda Fit (third generation) 36.4km / L DAA-GP5 type: FF cars "HYBRID"  Hybrid car
Daihatsu Miraisu 33.4km / L DBA-LA300S type: Full Grade  Gasoline light car (hatchback)
Toyota Prius 38.0km / L 32.6km / L DAA-ZVW30 type: "L"  Hybrid car (split system) hatchback sedan
Suzuki Arutoeko 32.0km / L 30.2km / L DBA-HA35S type: Full Grade  Gasoline light car (hatchback)
Honda Insight 31.0km / L 27.2km / L DAA-ZE2 type: "G", "L"  Hybrid car (parallel system) sedan
Daihatsu Move 30.0km / L 27.0km / L DBA-LA100S type: all grades of 2WD (FF) car  Gasoline light car (minivan)
Mazda Demio 30.0km / L 25.0km / L DBA-DEJFS type: "13-SKYACTIV"  Gasoline small car (hatchback)
Nissan Tiida 20.0km / L 18.0km / L DBA-C11 Type: "15S", "15M", "15G"  Gasoline small car (hatchback)
Suzuki EVERY 17.2km / L 16.4km / L EBD-DA64V type: 2WD ? MT cars "JOIN Turbo", 4WD ? MT car  Gasoline light car (one box van)
Mitsubishi ? RVR 17.0km / L 15.8km / L DBA-GA4W type: "M" 2WD "G" (FF) car  Gasoline ordinary vehicles (RV)
Nissan Serena 15.4km / L 14.6km / L DBA-C26 / FC26 type: "20X", "20G" 2WD of "Highway Star" (FF) car  Gasoline ordinary vehicles (wagon)
Nissan X-Trail 15.2km / L 14.2km / L LDA-DNT31 type: MT car  Diesel ordinary vehicles (RV)
〃 14.2km / L 13.8km / L LDA-DNT31 type: AT car Diesel ordinary vehicles (RV)
Honda Accord 14.4km / L 13.2km / L DBA-CU2 type: "20TL"  Gasoline ordinary vehicles (sedan)
Honda Odyssey 14.0km / L DBA-RC1 type: FF cars "ABSOLUTE"  Gasoline ordinary vehicles (minivan)
Mitsubishi Lancer Evolution X 10.8km / L 10.6km / L CBA-CZ4A type: "RS"  Gasoline sports car (existing car-based) sedan
Nissan ? GT-R 8.6km / L 8.7km / L DBA-R35 Type: all grades  Gasoline sports car (new design) coupe
For JC08 standard, the Prius consumption is 32.6 Km/l.
You are getting is only 20 km/L, which is very less (only 61.4%) of what is required. At least you should get 85 to 90%.
Get your vehicle inspected for better fuel economy.